e-cigarettes are growing in popularity as a means of quitting tobacco. An e-cigarette is the shape of a cigarette although it has a greater diameter than a regular cigarette and is heavier to hold. It delivers nicotine to the user, in varying amounts depending on the device used.
e-cigarettes also contain propylene glycol and vegetable glycerine. These may be used on their own or together and are the liquids that create the vapor.
When the user inhales on the e-cigarette, it causes a heating device to warm up a liquid contained in the cartridge. This creates the vapor that the user inhales and is why using an e-cigarette is called vaping.
e-cigarettes are commonly marketed as a healthier choice than smoking tobacco, as a helpful tool to quit tobacco and as a method of bypassing smoke-free laws as they only produce harmless water vapor.
It is reasonable to assume that using an e-cigarette is better for someone’s health, less hazardous to bystanders and less damaging to the environment.
Contra Indications For Using E-Cigarettes
Teenagers often start smoking cigarettes due to peer pressure. However, teens are now taking up smoking e-cigarettes rather than regular tobacco.
The Center for Disease Control and Prevention (CDC) reports the findings of a National Youth Tobacco Survey  showing that in 2011, 4.7% of high school students had used an e-cigarette. In 2012, that figure had more than doubled to 10.00%. In 2012, more than 1.78 million middle and high school students said they had used e-cigarettes. Studies  show that the majority of adults and teenagers who use e-cigarettes smoke regular cigarettes as well. Up to one third of younger e-cigarette users say they have never smoked a regular cigarette. These users are commencing an addiction to nicotine, albeit without the use of a tobacco cigarette.
Scientists from UC San Francisco analysed 84 research studies and other related material, into the health, behavioural and marketing effects of e-cigarettes. 
The scientists wrote that
“it’s a reasonable assumption that if smokers of regular cigarettes switch to e-cigarettes they would have a lower rate of disease caused by factors other than nicotine addiction”.
They found  that early research showed that e-cigarettes produced lower levels of plasma nicotine than regular cigarettes. However, more recent research showed that a person experienced in the use of an e-cigarette may gain the same level of nicotine absorption attained with a regular cigarette.
Pooling the results of five studies performed on population based smokers, the UCSF scientists discovered that smokers using e-cigarettes to quit tobacco were one third less likely to quit than people not using e-cigarettes. The researchers stated that it remains to be found whether e-cigarettes prevent quitting or whether people who use e-cigarettes are more dependent on nicotine and therefore find it harder to quit.
The UCS scientist concluded that
“the limited evidence shows that people making that switch also tend to progress to dual use of both e-cigarettes and regular cigarettes. This may result in a greater burden on public health”. They recommended that the use of e-cigarettes should be banned wherever the use of regular cigarettes is banned and e-cigarettes should have the same restrictions in marketing as regular cigarettes.
The basic ingredients of the liquid in e-cigarettes are propylene glycol and glycerine. A study  found that people exposed to propylene glycol may experience irritation of the eyes and respiratory system. If heated and vaporized, propylene glycol can make propylene oxide. This is classified as a Class 2B carcinogen by the International Agency for Research on Cancer. 
A study  into the short term pulmonary effects of using an e-cigarette measured the pulmonary function of healthy smokers. They smoked no tobacco cigarettes for four hours and then puffed on a Nobacco 11mg e-cigarette whenever they wanted to. The results showed no effects on spirometry tests. However, 18% of the subjects had an increase in dynamic airway resistance and 16% showed a decrease in the amount of nitric oxide that they expired. The study was limited by the small sample, the short time of not smoking tobacco, the short exposure time to the e-cigarette and the lack of comparison with smoking regular cigarettes. It is also known that smokers tend to have high airway resistance and lower levels of nitric oxide exhalation – both believed to be due to oxidant stress. However, the study does suggest that the use of e-cigarettes constricts peripheral airways. The researchers attributed this to the known irritant effects of propylene glycol. This could be a particular contra indication of the use of e-cigarettes by sufferers of asthma, emphysema or chronic bronchitis.
Flouris et al performed a similar study.  15 cigarette smokers used an 11mg e-cigarette (containing more than 60% propylene glycol) and a regular cigarette adhering to a specified protocol. The scientists also exposed 15 people who had never smoked anything to the vapor from an e-cigarette and smoke from a regular cigarette. The results showed that smoking a regular cigarette correlated with a significant decrease in the amount the lungs could expire. This result was not shown in those using an e-cigarette, or with those exposed to either regular tobacco smoke or e-cigarette vapor. Further analysis of data from this study  showed that after smoking a regular cigarette, white cell counts increased, indicating an inflammatory process. Those who used e-cigarettes and who were exposed to the vapor from e-cigarettes did not show a significant rise in white cells.
Schober et al  created an environment modelled on a cafe and then measured the indoor pollution created by 3 people using e-cigarettes for two hours. They found raised levels of nicotine, 1,2-propanediol, glycerine and aluminum, They also found 7 polycyclic aromatic hydrocarbons which the International Agency for Research on Cancer have classified as probable carcinogens.
An advocacy group for e-cigarettes, National Vaper’s Club, published a risk assessment  of using e-cigarettes and regular cigarettes. It concluded that vapor from e-cigarettes and smoke from regular cigarettes did not present a significant risk of harm to human health. However, the authors of the study did not detect benzoapyrene in regular cigarette smoke despite it being recognized as a known carcinogen. To say that it does not pose a significant risk, demonstrates fatal error in the data or their analysis of that date.
A report  funded by the Consumer Advocates for Smoke-free Alternatives Association used occupational threshold limit values to calculate the possible risks of various toxins in e-cigarettes. They concluded that there was no evidence to support that vaping produces aerosols that would warrant health concerns. However, threshold limit values are used to assess the health effects of occupational exposure to chemicals. These are commonly much higher than levels which would be acceptable for general exposure. By their nature, occupational chemical exposures do not consider subgroups such as people with existing medical conditions or children and babies who may be exposed to second hand e-cigarettes emissions, especially nicotine.
Positive Indications For Using E-Cigarettes
Propylene glycol has been thoroughly tested by the FDA who says it is safe. It is a common food additive which is also found in toothpaste, cough syrups and is also used in fog machines  in clubs and theatres. Vegetable glycerine is also considered safe by the FDA although there has not been much research done on it. The numerous flavors added to e-cigarettes are currently approved by the FDA for their inclusion in food. However, there is not enough information available about the safety of inhaling them. 
e-cigarettes do not burn as regular cigarettes do so they do not give off smoke. However, the user exhales an ‘aerosol’ which bystanders would be exposed to. The UCSF scientists looked at previous research  and found that aerosol from e-cigarettes has been found to contain measurable levels of toxins and nicotine. The toxins included formaldehyde, acetaldehyde and acetic acid. However, the levels were less than those emitted by regular cigarettes.
In a study by Schripp et al,  subjects used 3 e-liquids (apple flavor with no nicotine, apple flavor with 18 mg of nicotine and tobacco flavor with 18 mg of nicotine) and one regular cigarette. They also used different e-cigarette devices – 2 using a tank system (that is filled with e-liquid) and 1 using a cartridge filled with cotton onto which the liquid is dripped. They measured the levels of toxins and nicotine in the aerosols that were created. They found low levels of formaldehyde, acetaldehyde, isoprene, acetic acid, 2-butanodione, acetone, propanol, propylene glycol, and diacetin (from flavoring), traces of apple oil (3-methylbutyl-3-methylbutanoate). They also found differing levels of nicotine depending on the protocol used. All of these were emitted into the air. They concluded that aerosol from the e-cigarette had much lower emissions than regular cigarettes.
Czogala et al  conducted a study regarding second hand exposure to the aerosol from e-cigarettes and regular cigarette smoke. They found that while bystanders would be exposed to nicotine, the levels would be one tenth of those found in regular cigarette smoke. They also found that the aerosol from e-cigarettes was not a source of exposure to carbon monoxide, whereas smoke from a regular cigarette was.
A study published at the end of August 2014 found that second hand vapor given off by one brand of e-cigarette contains less dangerous chemicals than the smoke from a regular cigarette. In the most recent study, researchers analyzed the air in an office, ironically at a cancer research center n Milan, Italy. Two men and one woman smoked either regular cigarettes or vaped an e-cigarette called Ovale – a brand sold worldwide. They found that particulates – hazardous substances found as liquids or solids – were ten times higher in the smoke from a regular cigarette than from the vapor of an e-cigarette. The study did not examine which chemicals were inhaled by bystanders and only researched smoking indoors, which is widely banned in the U.S. The author of the study, Arian Saffari (a graduate student and fellow with the department of civil and environmental engineering at the University of Southern California) said that the findings indicated that
“generally speaking, e-cigarettes are safer than traditional cigarettes.”
The vapor from the e-cig was found to contain levels of heavy metals. The researchers think that the chromium and nickel may have been released into the air by the metal cartridge that holds the liquid nicotine solution in the e-cigarette. Saffari said that
“in terms of their effects on health, some of these metals are highly toxic, even in tiny amounts. Manufacturers of e-cigarettes could limit the amounts of heavy metals in the vapor by making the cartridges from materials of a higher quality”.
However, Doctor Peter Hajek (a professor of clinical psychology at St. Bartholomew’s Hospital and The London Queen Mary’s School of Medicine and Dentistry at the University of London) is not alarmed by the levels of heavy metals found in the vapor of e-cigarettes. Hajek, who studies the risks of tobacco, said
“the study showed that e-cigarettes contain none of the most hazardous chemicals found in regular tobacco smoke”.
He noted that other chemicals contained in e-cigarettes are still a tiny fraction of those found in regular cigarettes and that although metal compounds are released by an e-cigarette, the amounts are to small to be likely to carry a risk. Hajek concluded that e-cigarette vapor is unlikely to be of any risk to bystanders.
George Conley (President of the American Vaping Association) said
“the level of heavy metals and other various chemicals found in the vapor of e-cigarettes is similar to that of other inhalable products meant to help people quit smoking – in particular the Nicorette Inhaler which has FDA approval”.
Conley concluded that the study (as well as many more studies) has found
“clear evidence that e-cigarettes are far, far less hazardous than smoking, likely in the range of 98 to 99%”.  
It’s difficult to draw conclusions when comparing studies because relatively few have been done. Those that have, focus on only one or two aspects of using an e-cigarette and so the results are either clearly in favour of, or against their use. For example, the heat created when the user of an e-cigarette inhales, is known to create chemicals that are potentially harmful. However, these amounts are between 9 and 450 times lower than the chemicals in regular cigarettes. The huge difference in known amounts stems from the enormous numbers of models, types and brands of e-cigarettes. The differing amounts of chemicals in all of these make it very difficult to make any overall conclusions about the safety of e-cigarettes.
There’s no doubt that e-cigarettes are causing heated debate. All health care professionals agree that that smoking tobacco causes disease and deaths. However, they don’t agree if e-cigarettes are helping to reduce that problem or could potentially make it worse.
Opponents of e-cigarettes say that one of the problems with them is that they contain nicotine and because nicotine is so addictive, e-cigarettes could be paving the way for youngster currently vaping to move onto smoking regular cigarettes. They also dislike the use of candy flavors for vaping as they say the manufacturers are targeting youngsters. It also makes it harder for parents to know if their children are vaping because the fruity flavors on their breath give no clues as to what they’re doing.
This, combined with the massive marketing of vaping targeted at young people makes opponents fear that the number of people smoking regular cigarettes could start to rise, after decades of declining.
Others cite the potential benefits of e-cigarettes, saying they are a much safer option for smokers of regular cigarettes. However, research does not show that they are of any particular benefit for those wanting to quit.
To summarize, relatively few studies have directly addressed the effects on health of e-cigarettes. Many more studies (and much larger ones) are clearly warranted. The studies must also be impartial with no vested interest in the tobacco or e-cigarette industries.
Finally, it is impossible to establish the long term effects of e-cigarettes on health as they are relatively new. They have not been widely used for long enough to establish a meaningful assessment.
Although research into the effects of e-cigarettes on health is growing, the FDA website says that it currently only regulates e-cigarettes that are “marketed for therapeutic purposes.” However, it has issued a proposed rule  (Tobacco Products Deemed to Be Subject to the Food, Drug & Cosmetic Act – Deeming) to extend the authority of the FDA Center for Tobacco Products (CTP) to cover “additional products that meet the legal definition of a tobacco product, such as e-cigarettes.”
The World Health Organization (WHO), the American Heart Association (AHA) and the Food and Drug Administration (FDA) are all calling for e-cigarettes to be regulated.
The AHA noted on their blog  that e-cigarette advertising targeted at young people rose an astonishing 250% from 2011 to 2013. It’s now thought to be reaching around 24 million youngsters.
Not surprisingly, the AHA wants the FDA to ban both the marketing and the sale of e-cigarettes to young people who have been using e-cigarettes in increasing numbers. The FDA proposed a rule in April 2014 that would let it regulate e-cigarettes in the same way that it does for regular tobacco products. However, that proposal is still waiting to be finalized.
Smoking tobacco is implicated in around 5 million annual deaths worldwide. Cigarettes give off an estimated 4,000 chemicals while they’re being smoked. Just a few of these chemicals, such as arsenic, formaldehyde and lead are known to trigger cancer as well as many other potentially fatal diseases.
The huge increase in the popularity of e-cigarettes used by adults to help them quit tobacco and by teenagers has meant that the e-cigarette industry is now worth around $1.5 billion. Estimates are that it could double to $3 billion in the next 5 years. This is a huge market and manufacturers of e-cigarettes will obviously want people to keep using them.
Having assumed that e-cigarettes would be safer and less harmful to the environment then regular cigarettes, it was surprising to find how many studies concluded with contra indications for the use of e-cigarettes.
What is clear, is that many more studies are needed to help potential users of e-cigarettes make an informed choice.
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